+ userfaultfd-selftests-modify-selftest-to-use-dev-userfaultfd.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: userfaultfd: selftests: modify selftest to use /dev/userfaultfd
has been added to the -mm mm-unstable branch.  Its filename is
     userfaultfd-selftests-modify-selftest-to-use-dev-userfaultfd.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/userfaultfd-selftests-modify-selftest-to-use-dev-userfaultfd.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Axel Rasmussen <axelrasmussen@google.com>
Subject: userfaultfd: selftests: modify selftest to use /dev/userfaultfd
Date: Wed, 1 Jun 2022 14:09:48 -0700

We clearly want to ensure both userfaultfd(2) and /dev/userfaultfd keep
working into the future, so just run the test twice, using each interface.

Link: https://lkml.kernel.org/r/20220601210951.3916598-4-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Charan Teja Kalla <charante@codeaurora.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dmitry V. Levin <ldv@altlinux.org>
Cc: Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/vm/userfaultfd.c |   37 ++++++++++++++++++---
 1 file changed, 33 insertions(+), 4 deletions(-)

--- a/tools/testing/selftests/vm/userfaultfd.c~userfaultfd-selftests-modify-selftest-to-use-dev-userfaultfd
+++ a/tools/testing/selftests/vm/userfaultfd.c
@@ -77,6 +77,9 @@ static int bounces;
 #define TEST_SHMEM	3
 static int test_type;
 
+/* test using /dev/userfaultfd, instead of userfaultfd(2) */
+static bool test_dev_userfaultfd;
+
 /* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
 #define ALARM_INTERVAL_SECS 10
 static volatile bool test_uffdio_copy_eexist = true;
@@ -154,12 +157,14 @@ static void usage(void)
 			ret, __LINE__);				\
 	} while (0)
 
-#define err(fmt, ...)				\
+#define errexit(exitcode, fmt, ...)		\
 	do {					\
 		_err(fmt, ##__VA_ARGS__);	\
-		exit(1);			\
+		exit(exitcode);			\
 	} while (0)
 
+#define err(fmt, ...) errexit(1, fmt, ##__VA_ARGS__)
+
 static void uffd_stats_reset(struct uffd_stats *uffd_stats,
 			     unsigned long n_cpus)
 {
@@ -383,13 +388,31 @@ static void assert_expected_ioctls_prese
 	}
 }
 
+static void __userfaultfd_open_dev(void)
+{
+	int fd;
+
+	uffd = -1;
+	fd = open("/dev/userfaultfd", O_RDWR | O_CLOEXEC);
+	if (fd < 0)
+		return;
+
+	uffd = ioctl(fd, USERFAULTFD_IOC_NEW,
+		     O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
+	close(fd);
+}
+
 static void userfaultfd_open(uint64_t *features)
 {
 	struct uffdio_api uffdio_api;
 
-	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
+	if (test_dev_userfaultfd)
+		__userfaultfd_open_dev();
+	else
+		uffd = syscall(__NR_userfaultfd,
+			       O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
 	if (uffd < 0)
-		err("userfaultfd syscall not available in this kernel");
+		errexit(KSFT_SKIP, "creating userfaultfd failed");
 	uffd_flags = fcntl(uffd, F_GETFD, NULL);
 
 	uffdio_api.api = UFFD_API;
@@ -1691,6 +1714,12 @@ int main(int argc, char **argv)
 	}
 	printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
 	       nr_pages, nr_pages_per_cpu);
+
+	test_dev_userfaultfd = false;
+	if (userfaultfd_stress())
+		return 1;
+
+	test_dev_userfaultfd = true;
 	return userfaultfd_stress();
 }
 
_

Patches currently in -mm which might be from axelrasmussen@google.com are

mm-userfaultfd-fix-uffdio_continue-on-fallocated-shmem-pages.patch
selftests-vm-add-hugetlb_shared-userfaultfd-test-to-run_vmtestssh.patch
userfaultfd-add-dev-userfaultfd-for-fine-grained-access-control.patch
userfaultfd-selftests-modify-selftest-to-use-dev-userfaultfd.patch
userfaultfd-update-documentation-to-describe-dev-userfaultfd.patch
userfaultfd-selftests-make-dev-userfaultfd-testing-configurable.patch
selftests-vm-add-dev-userfaultfd-test-cases-to-run_vmtestssh.patch